Walking through the forest, you become aware of another presence. For a while there's nothing there but birdsong and the odd drone of a distant plane. But in the occasional silences it becomes evident that something – several things – have been here before you. Every few yards, the earth has been gouged up and pushed aside, the leaves freshly dishevelled. At the base of the beech trees are long, raking scratches where some creature has ripped over the topsoil, looking for something beneath. Bluebell roots lie scribbled against the earth where they've been pulled up and cut through, and around the base of the larger trees are deep, pale craters, as if the forest had recently been surprised by a shower of small meteorites.

The animals responsible for all this re-arrangement have long gone. They're nocturnal and nomadic, and their recent notoriety has made them shyer than usual. By day they retreat into the secret parts of the Forest of Dean and by night they move from place to place, rooting their way to subterranean treasure and – just as likely – an early grave.

It isn't easy being a wild boar in Britain these days. Having been deliberately reintroduced a couple of decades ago, they've found themselves staring down the wrong end of our conflicting attitudes towards wildness. We wanted them because they once belonged here. We didn't want them because they're disruptive and piggish. We like them because they're charming and tasty. We don't like them because they're untidy. We're keen to take their picture, but we'd prefer them dead.

Now, having settled in nicely, the wild boars find themselves accused of everything short of satanism. Walkers say they live in fear of boars attacking them or their dogs. Farmers complain of thousands of pounds' worth of damage done to crops, fences flattened, maize laid waste. Homeowners have their lawns dug up and their gardens destroyed. And many people fear what inevitably follows the boar: the poachers and the men with guns.

Is it realistic to bring back an animal that hasn't lived in Britain since Henry VIII was out hunting? Are boars better managed by Defra and the Forestry Commission, or by private landowners with high ideals and land to spare? Should they be hunted, should they be farmed, and can they ever just be left to get on with being themselves? And what exactly do we want boar for?

The beaver and the boar were both hunted to extinction in Britain more than 400 years ago, though elsewhere they continue to thrive – 750,000 boar are killed each year in mainland Europe. In many areas, they have become a public menace: the city of Berlin culls 2,000 "feral" boars annually. Like foxes, boars have realised that there are excellent pickings to be had from the bins of urban Germans. Unlike foxes, they also have a habit of smashing through shop windows, rooting up football pitches or trashing cemetery grounds.

Since a full-grown sow can weigh more than 150kg, they can be an intimidating presence, even if no wild boar will attack humans unless provoked. Most domestic pigs, bred and interbred over centuries, end up looking like office furniture, but a wild boar looks more or less like a pig ought to. They've retained their original shape – rounded back; sticky-up ears; long, delicate legs – as well as much of their individuality and intelligence. A mature sow is front-loaded: all power in the head and chest, a miniature Picasso bull.

Back in the mid-1970s, a few farmers in southern England began importing wild boar from eastern Europe to farm for meat. After a while, some of those boars escaped. They were joined by boars dumped by illegal importers, set free by animal-rights activists or released by hunters for sport. By the millennium they were flourishing, particularly in areas such as the Forest of Dean that offered ideal conditions: rich, deciduous woodland, agricultural land nearby and the occasional bin to raid. Separate breeding populations established themselves in Kent, Sussex, Dorset, Gloucestershire and Scotland. Their fans cited their charm and their regenerative effect on the soil. Their detractors pointed to the havoc they could cause.

Defra spent three years producing an "action plan" which established that the boars were in fact wild boar rather than pigs in fur coats, and laid the responsibility for dealing with them on local communities and landowners. They also maintained their classification as dangerous wild animals, a category that also includes Tasmanian devils, death adders and Brazilian wolf spiders. That classification means that owners must hold a licence for wild boar, and that owners or farmers can be prosecuted if their boars escape.

In the Forest of Dean a cull was introduced – 30 boars the first year, 60 the second, 122 in 2011. The only trouble is that no one, not the Forestry Commission, not Defra, not the scientists or the experts, has any idea how many animals are actually out there; despite the use of increasingly sophisticated military thermal- imaging equipment, no one has yet managed a definitive count. Talk to the landowners and hunters and there's a boar bristling behind every shrub. Talk to the foresters and there's only an oppressed handful remaining.

Josh Theobald, head keeper on the nearby Lydney estate, has seen the boar at work. "If they find something they like, they hammer hell out of it, snuffling and rooting, knocking up turf. Their nose looks soft, but they're hellish strong. They'll eat anything, pretty much. While I was trying to shoot one three years ago, it ate some corn out of a feed-hopper, a squirrel out of a trap and when I actually shot it, it was pulling up a tree root. I mean, they're impressive."

Foresters describe watching families of boar push through ground that has been snowed over and frozen for several days, overturning the hard earth with their snouts as if it were soft as sand. "They're always wallowing in mud – typical pig," says Theobald. "When you shoot them, you get a puff of dust coming off them, because their coats are just full of soil. When they're rotavating, they're looking for earthworms, beetles, roots, but they'll eat meat, vegetables, maize – anything. That's obviously why they do so well. The ones we've shot have been in hellish good condition."

There is no closed season for boar – no period during the year when shooting them is illegal – so they have the same legal and moral status as rabbits, pigeons and grey squirrels. "The one I shot, it was huge," says Theobald. "Eight and a half foot long hung up. It took four of us to lift it into a truck. There's a layer of fat about two inches thick all over, and when you shoot them it's a bit like shooting a concrete block – they are solid." And it's good meat? "Oh, very good meat. I mean, everything we shoot, people are crying out for it."

Anything shot on the Lydney estate gets tested for TB and trichinella worm and certified by Defra before being sold through an official game dealer. But others are not so scrupulous. With the increase in interest in boar comes a corresponding increase in poaching. Pepi Barrington, who breeds Irish water spaniels in the forest, is constantly aware of their presence. "The number of boar has definitely gone down. That's not because of the FC [Forestry Commission], it's because of poachers. There's been so much publicity with Autumnwatch and Springwatch, and all these TV programmes that poachers come from far and wide."

Barrington is as alarmed by the poachers as she is by the boars themselves. "There will be poachers out tonight, I can guarantee it. I see the lights and the tyre tracks. The police know who they are, and they won't do anything. Unless it involves someone being injured, poaching is not high on their list of priorities." This isn't old-style stealing for the pot; it's large-scale killing to order, and the poachers aren't picky. They take all sizes and ages, including lactating females with young piglets. They'll also take roadkill. By the time FC rangers set out to a boar injured or killed in traffic accidents, the victims will already be in the back of a van on their way to a roasting pan.

"You used to see boar in broad daylight, but you don't much any more," says Barrington. "Because they've been shot at a lot, harassed by people – all these bloody wildlife photographers, the place is crawling with people trying to photograph them – because of that they've gone into the thicker areas and they're becoming more and more nocturnal."

Two of her dogs were attacked by a lone male boar a couple of years ago as she was walking through the woods. "I'd just gone over a stile and all of a sudden this boar appeared from nowhere and shot past me. That's all I saw – this huge thing hurtling past with tusks. He went after two of the dogs – one of the Irish water spaniel bitches and the labrador. The spaniel turned round to look at me and the boar took a huge chunk out of her rear end. It got the labrador as well."

Both have subsequently recovered, but Barrington now puts bells on all her dogs' collars, so a walk in the woods sounds like a stroll with a herd of Alpine goats. The problem, she thinks, "is that the local community is so divided – some people think they're wonderful and that it's a great privilege to see this animal that was hunted to extinction. But people who actually use the forest find them quite dangerous."

In other parts of Britain, anyone who has the inclination, space and the licence can bring in boar on their own land to farm or to run free. Paul and Louise Ramsay, who own the 13,000-acre Bamff estate in Perthshire, have spent the past decade on a wildlife regeneration scheme involving wild boar and Norwegian beaver. Back in 2002, two beavers were released on the estate, followed a few months later by six wild boars. They liked what they saw. And since both also had very specific exterior design requirements, they immediately embarked on an ambitious relandscaping plan for Bamff. Boars generally favour a Somme-style ambience, while beavers prefer a really large stage on which to work. In the decade since they arrived, both species have done their best to convert large areas of Bamff back from 18th-century parkland into late-Pleistocene swamp.

The boar and the beaver coexist contentedly, the boar in fenced enclosures and the beaver busy with large-scale forestry operations and novelty woodwork. The boars like the beavers' new terraced ponds. "They love to wallow, so they love wet muddy places," says Paul. It is the authorities who are less easily pleased. According to Louise, SNH (Scottish Natural Heritage) now wants to remove all Scottish beavers. "So I started a campaign called Save the Free Beavers of the Tay on Facebook." Paul laughs: "We did get quite a lot of people. Not all of them interested in animals."

Both Paul and Louise had always been interested in conservation and ecology, so when Paul was offered a few wild boar on a visit to the Scottish Borders a decade ago, he took the bait. "I understood that I was getting three gilts – virgin females, I suppose you'd say. And then it turned out that far from being three gilts, there were six of them: three females, two males and an intersex." Intersex? Does he mean a hermaphrodite? "Well, yes. It was slightly awkward, because this boar, which definitely thought of itself as the alpha male, would knock the other chaps off the job, but then he couldn't serve the females himself." Why not? "He didn't have the equipment. He was also rather aggressive, so he got shot."

Ten years later they now have around 80 boars in three separate large enclosures, fed once a day but otherwise left to themselves. Their meat is sold locally and online as joints, sausages and "boargers". The main issue is keeping them in. Boar will root under conventional fencing and electric wires can short out – so to begin with they did have problems with escapees. As Louise says: "What we say to our neighbours is that if a boar does break out and they find them on their land, then they're more than welcome to shoot it and make it into sausages, because that seems a reasonable deal to us. But I think if people understand how to manage wild animals and they don't feed them or dysfunctionally hunt them, then humans not only can but must coexist, because the alternative is that we live in a monocultural desert."

At the time wild boar were originally hunted to extinction, the British population was 6 million. Now it's 60 million. Since they've returned, they've behaved exactly as wild boar are supposed to behave; the clue, after all, was in the "wild" part. It's us – the dog walkers, the hunters, the poachers, the landowners, the government and the experts – whose behaviour has been divided and erratic. If we couldn't coexist with the boar 400 years ago, what makes us think we can now? And where, in this insatiable island, is there ever going to be space for something other than us?

A little further down the road, Andrew Johnston has been farming wild boar as a full-time business for 17 years, and has 40 breeding sows on a hillside just outside Perth providing a steady supply of meat for the local market. A decade ago, he says, eating wild boar was a novelty; now it's part of our rising appetite for game. The meat is unexpected – not rich and porky but lean and very flavoursome, almost like venison. In Johnston's view, the British are getting a taste for it. "There is a demand," he says, "but it's specific. Mostly I get repeat customers who come to the farmers' market week in, week out. They want something better than normal pork, something more interesting."

It was one of his boars, McQueen, which in 2002 escaped from a pen at the abattoir, swam the river, scampered across Dunblane golf course and, despite a full-scale hunt involving the emergency services, an armed-response team and a televised plea for McQueen's life by the actors Martin Shaw and Jenny Seagrove ("This pig wants to live"), evaded his captors and fled into the Highlands.

"I'm not sure where he ended up," says Johnston. "But I suspect probably in someone's freezer."

The boar facts

Wild boar became extinct in the UK in the 17th century.

There are thought to be between 500 and 1,000 animals in the UK currently. The biggest populations are in Kent, East Sussex and the Forest of Dean in Gloucestershire, with others in Devon, Bedfordshire, Dorset and Scotland.

Adult boars can stand up to 1m tall at the shoulder, with adult males weighing up to 150kg. Both sexes have tusks. Female and young boars live in groups; fully grown males tend to be solitary. Sows give birth to litters of between five and seven piglets once a year.

Boars should not be approached, as they can be dangerous, especially if guarding piglets.

Following the extinction of wolves and lynxes in the UK, boars have no natural predators except humans.